Don't be a midiot. Understand it's basic. In, Out, Thru, MTC, Midi Channels, Sysex, Control change.
I,O,T Lesson 1: If you're tapping in to a soundmodule to hear it's sounds, whether by controlling it from another little keyboard, or a computer sequencer, or whatever, you're going to literally tap IN to midi IN on that sound module. For using a module (which may be a keyboard, effects unit, or any device with midi) as a midi controller eg. keys, sliders, wheels, sequencer, arpeggio, etc... you must send that info OUT by using the MIDI OUT, the other end of the cable is tapping IN to the module being controlled. Thru will simply give you an extension of the MIDI data coming IN (MIDI IN,) from a controller (sending MIDI OUT.) MIDI THRU connects another module in a chain, THRU to IN. This way, the controller which is sending MIDI OUT will go IN to the first module and control it, and also via the THRU, another cable will go IN to the second module and also be controlled. This chain can go on for about 4 times before a latency known as midi delay begins to occur, causing sluggish timing and response.
MTC, Lesson 2: Midi Time Code is the common timing all your modules will share in sequencing. If your sequencer generates MTC, then it will send it's code to other sequencers and lock up into syncronization with them. It can also be used for syncing LFO rates, panning, and whatever else that has capability of recieving MTC.
Midi Channels, Sysex, Control change. Lesson 3: Midi ch. are the lanes that carry the midi data back and forth from controller module to slave. The data is able to send and recieve only when the modules interacting are set to the same midi channel. Sysex, is a codified method of tranfering data to control modules by commands in the form of strings of letters and numbers. Some sequencers let you see these commands for you to edit if neccesary. Sysex is an exclusive code understood only by a particular module, and is not a universal language to all other modules. C.C. or control change, on the other hand is universal according to a standard, and refers to extra midi channels called C.C. messages. These are extra midi lanes which are program specific to certain commands, such as volume, pan, tremelo, etc... If you are able to designate a midi C.C. # for your slider or bender for instance, to send MIDI OUT to a module, then it will control whatever C.C. message (volume, pan, tremelo, etc.)that has the same C.C. #.
This may be too basic, of course, so I suggest going to HARMONY CENTRAL to learn more about midi. Also try SYNTH ZONE. SysEx isn't as important to understand at first, since a lot can be done with C.C. But as you experiment and demand more from midi, you will enter into SysEx. Hands on by using your gear and manuals will teach you everything you need to know
Cheers!
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-AT
Beethoven can write music, thank God, but he can do nothing else on earth.~ Ludwig Van Beethoven